Projection devices including both front display and rear display systems generally include one or more optical elements. These optical elements may include lenses and redirecting elements such as mirrors for processing, redirecting, and focusing light onto a display surface. In some projection devices, a relay lens and mirror may be arranged within the light path to transfer and focus light received from a light source onto an image-producing element (such as a microdisplay) for image creation. The image-producing element may then be configured to redirect light toward a projection lens.
Some projection devices may be configured to have a reduced size along one or more dimensions compared to conventional devices. For example, thin rear projection devices are configured to have a reduced depth so that the display may be mounted to a wall or like surface. Likewise portable front projection devices may have reduced size along one or more dimensions for increased portability. However, the arrangement and size of the optical elements used in these devices may impose a lower limit on the dimensions of the devices. For example, the use of a single relay lens may allow the construction of a smaller or thinner projection device relative to the use of a pair of relay lenses. However, the power of the single relay lens may have to be increased to achieve the same optical effect as the pair of relay lenses. The higher power single lens may be larger and more expensive to construct, and may therefore limit the size and increase the cost of a projection device.